FNA diagnosis of giant cell fibroblastoma: a case report of an unusual pediatric soft tissue tumor.

Giant cell fibroblastoma (GCF) is a rare pediatric soft tissue tumor, which exists on a spectrum with dermatofibrosarcoma protuberans (DFSP). Histologic features are well established for these entities; however, cytologic findings have not been well characterized. We report for the first time a case of GCF, confirmed by cytogenetics, with mixed DFSP features. In this case of an 8-month-old boy, a fine needle aspiration specimen showed a low-grade spindle cell tumor, with oval to spindled cells dispersed singly and in patternless groups, and with occasional giant cells. Subsequent histologic features were consistent with GCF, which is an uncommon, CD34 positive, soft tissue neoplasm with a distinct molecular aberration. This case emphasizes the differential diagnosis in pediatric soft tissue tumors and stresses the unique features of GCF.